Electric control



l. E. MCCABE LECTR I C CONTROL sept. 5, 1939.

2 Sheets-Sheefl Origi'nal Filed April 18 mlmmmnv 23 ,a

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Hill/lll THE/M105 TAT/f MEM L Sept. 5, 1939. E. MccABE 2,171,859

ELECTRIC CONTROL Original Filed April 18, 1935 2 Sheets-Sheet 2 NVENTOR. /A f. MCC/7Bf BY M ATTORNEY.

Patented Sept. 5, 1939 UNITED STATES PATENT OFFICE original application April 1s, 1935, seriaiNb. 17,073, now Patent No. 2,075,951, dated April Divided and this application January 2, 1937, Serial No. 118,720

4 Claims.

This invention relates to improvement in electric controls and to a simplified device for such controls wherein it is desired to open the circuit after a predetermined time in case of failure of 5 certain functions of other devices in the control or controlled circuit, and more particularly to that type of device used to stop the equipment upon failure ofv combustion or ignition in fluid fuel burners.

In a number of previous applications, this applicant has disclosed various methods and means of producing such devices, many of which have attained considerable commercial use. One form disclosed in Patents Nos. 1,686,286 of. October 2,

1928, and 1,690,689 of November 6, 1928, comprised a normally open switch with detachable means for holding the switch in closed position releasable by heat, generated by an electric current, including means for varying the current passing through said heat generated means in accordance with temperature or 4pressure changes.

Another form disclosed in this applicants Patent No. 1,681,421 of August 21, 1928, involved the use of a similar thermal safety device included in a circuit to a fluid fuel burner wherein the heat. generated means for releasing the safety switch was constantly energized during the operation of the burner and means included, operable upon the establishment of combustion, to divert a stream of air from the burner draft tube, produced by the burner fan, to cool the heat generated means.

Still another form, and one which has been successfully applied to the extent of wide commercial use, is disclosed in this applicants Patents Nos. 1,675,897 of July 3, 1928; 1,648,390 of November 8, 1927; 1,884,045 of October 25, 1932; 2,015,952 of October 1, 1935, and 2,024,697 of December 17, 1935, which incorporated the use of electrically operated thermally actuated safety releases in combination with switching means operating under certain conditions to establish a shunt circuit by which the current may be bypassed around the electrically operated thermal release.

Although the devices wherein the shunting circuit is employed are being commercially adapted in one form or another in electrical controls of the character herein disclosed, they have presented problems when attempts to apply them to certain classes of applications have been made. as well as leaving room for improvements in their more common applications.

When the heat generating means is in series (Cl. Zoll- 122) with the load, and the operating requirements of such loads as solenoids or magnetically operated devices is small, after starting, the impressed voltage on the load is increased when the shunt circuit is closed, and the load is thus subjected to additional current. A reverse of this characteristic would be more suitable or desirable as an increase in resistance of the circuit would limit the currentinstead of it being increased as it is in the shunt circuit applications heretofore re- 10 ferred to. Furthermore, the heat generating means upon being shunted out naturally cools and in the event the shunt circuit is caused to open, as in the case of flame failure during the operation of a fluid fuel burner, the time required to effect the release of the safety switch necessitates the heating of the heat generating means which, however short as it is possible to make that period, may nevertheless be of such duration that should the flame extinguishment have ,o been caused by an air pocket or sludge of water in the fuel supply line, the burner, which continues to operate, would permit fuel to be admitted to a hot combustion chamberwithout immediate means to ignite it, thus producing a haz- 25 ardous condition for a longer period of time, than with the method herein disclosed.

The advantages of using mercury switches as circuit breakers are well known. but their use in electrical circuit controls, such as disclosed in 30 the aforementioned patents, particularly Nos. 1,675,897 and 1,884,045, require considerable mechanism for the development of the power and means to operate them, or speciallyv designed shunting devices, as shown in Patent No. 1,648, 35 390, so that in recent years there has been a trend toward producing controls of the disclosed character employing open contacts, even though they are inferior to mercury switches, being less durable and dependable and subject to pitting, 40 sticking and corrosion, solely through the necessity of meeting the demand in some quarters for cheaper controls, as they represent a major item in establishing the cost of oil burner installations.

It is, therefore, an object of this invention to 45 provide a simple device which may retain the use of a mercury switch as a circuit breaker, if desired, and of such construction as to dispense with the need of costly power producing mechanisms, and further', to eliminate the shunt cir- 50 cuit, and instead, to provide means whereby the relationship between the releasable switch holding means'and the electric thermal actuating means may be changed or one'shielded from the other during normal running operation. By

this method, the heating element may be constantly energized during the operation of the controlled device, or mechanisms, and, if for any reason during that period should the elements comprising the safety mechanism bc caused to assume their normal starting positions.

a much shorter period of operation is thus attained in effecting the release of the safety switch than possible with the shunt circuit wherein only a substantially constant tripping period is possible at any time upon, or during, a demand for operation of the controlled device, it being necessary to allow a sufcient tripping time to permit the burner to start normal operation when the furnace is cold as the oil may be slow in reaching the combustion chamber due to the necessity of the pump having to bring it from a remotely located tank.

By means of this invention, it is possible to reduce to a minimum, which probably will not be exceeded, the number of contacts heretofore found necessary in controls of this character to make and break a circuit to meet the greater number of applications. The simplicity of construction, which this feature affords, makes possible its use as areliable control of great utility in elds where it is adaptable. This application is a division of this applicants prior copending application Serial No. 17,073, led April 18, 1935, and which matured into Letter Patent No. 2,075,951, of April 6, 1937.

With these and other objects in view, reference is made to the accompanying drawings which illustrate preferred forms of this invention with the understanding that detail changes may be made without departing from the scope thereof.

- In the drawings:

Figure 1 is a fragmentary view partly in side elevation and partly in section of an embodiment of this invention.

Figure 2 is a view in front elevation of Figure 1 illustrating` the parts in their normal starting position.

Figure 3 is a detail top plan view of the front carrying plate and the mechanism mounted thereon including the tripping means for the tube switch less the heating element.

Figure 4 is a View of the parts illustrated in Figure 2 showing the heating element in inoperative position.

Figure 5 is a view similar to Figure 4 showing the position of the parts after the tube switch has been tripped by the heating element.

Figure 6 is a detail gew in front elevation of the actuator for the heating element.

Figure '7 is a schematic wiring diagram of the circuit controlled by the device illustrated in Figure 2.

The embodiment of this invention as illustrated is adapted to control the operation of a motor such as is employed to operate the mechanism of a uid fuel burner, and is responsive to combustion conditions of the furnace to which the fluid fuel burner is applied, to trip the safety switch by means of changing the relation of a heating element and the thermostatic member of an electrical control such as disclosed in this applicants prior Patent No. 2,024,697, of December 7, 1935, and in so doing combines the motor and safety switch in one three-terminal mercury tube switch. The switch mechanism is mounted upon the base plate I which may vform the bottom of an enclosure, not shown. To the rear-of the base plate I a tubular member 2 is secured which is adapted to enter and be attached to the stack leading from the furnace to the chimney in the usual manner. The free end of the tubular member 2 mounts one end of a vspiral or helix of bi-metallic or thermal metal 3 which is secured thereto by the screw 4. The free end of the coil or helix is secured to the outer end 5 of an operating shaft 6 arranged axially of the tubular member 2. The base plate I is provided with a circular opening I within and concentric to tubular member 2. A hollow cylindrical member 8 is mounted to rotate freely within the aperture 'I. The inner end of the shaft 6 mounts the member 8 and the actuator for the heat element, as shown in Figure 6, and imparts an oscillatory movem-ent to the member 8 and the switch carrying plate 9 upon contraction or expansion of the coil or helix 3 in response to combustion conditions within the furnace.

The secondary coil I0 of the repulsion relay is carried by means mounted upon a pivot stud II in the same manner as disclosed in said prior application and inasmuch as the mechanism cooperating between the operating means for the carrier plate 9 and the secondary coil I0 is the same as that shown in said prior Patent No. 2,024,697, it is not thought necessary to further describe these parts herein.

The arm I 2 extending from one side of `the coil I0 and which is pivoted on the pivot stud II is provided with a depending angular termination I3 to which is pivoted on a switch carrier plate I4 which mounts in the clips I5 a three-terminal mercury tube switch I6, shown in detail in Figure 5. This switch is held in its Ynormal operating positions substantially parallel to the arm I2 of the carrying means for the coil I0 by providing an extension II to the carrier plate I4 with an angular, upwardly extending member I8 which mounts at its free end a catch pin I9 normally adapted to engage under the nose of a latch member 2| mounted to rotate about a pivot post 22 in conjunction with a tripping plate 23 mounted thereon. The post 22 is mounted between plates 26 and 26a held in parallel spaced-apart position by posts 24 and 28 and secured to the front plate 2l by screws 28a. The tripping plate 23 is provided with a slot 25 through which the post 24 passes to limit the movement of said tripping plate about its pivoted point.

A bi-metallic or thermal member 30 in the form of a plate is secured at its lower end upon the tripping plate 23, as shown. A thermal member including a circular portion 3I and spacedapart parallel portions 32 and 33 extending therefrom is mounted in the position shown in Figures 3 and 5 with its shorter end 33 clamped upon the plate 26. 'Ihe free end of the portion 32 mounts a catch pin 35 adapted to be engaged when cold by' the member 30 when the switch I6 is in the normal open or closed position and with the nose of the latch 2I in engagement with the catch pin I9. A guide rod 36 is mounted concentric with the axis of the curved portion 3I of the thermal member upon a bracket, as shown in Figure 2, secured to the rear side of the front plate 21. A heating element including a spool 40 wrapped with electrical resistance wire 4I is mounted to reciprocate upon said guide rod 36 to be received entirely Within the circular member 3| of the thermal member and to be withdrawn 70 2, the heating element is received entirely within the circular portion 3l of the thermal member, and in rotatingfrom this position to the position shown in Figure 4, the extension 42 engaging the ange 44 of the heating member moves the heating member over the guide rod 36 to withdraw it entirely from the thermalV ltripping plate 23 is released and the free end thereof will rotate downwardly until the end of the slot engages the stud 24 and in so doing will cause the latch 2| to be released from engagement with the catch pin I9 whereupon the safety switch I6 is rotated about the pivot of the carrier plate I4 to assume a position shown in Figure 5 in which the circuit is open through all of its terminals. 'Ihe latch 2| is caused to rotate about its pivot post 22 in conjunction with the tripping plate 23 by forming the end of the tripping plate 23 on the side of its pivot post most distant from the stud 24 with an angularly extending termination 45 and providing the latch 2| with an extension from its upper end integral therewith whereby when the tripping plate 23 has been rotated so that its member will' be engaged by the catch pin 35, the nose. 20 will be adapted to engage the catch pin I9 and support it in the axis of the pivot stud II.

The mercury tube switch I6 is provided with terminals 46 and 41 entering from opposite ends both of which will be submerged in the mercury '49 when the switch'is held in the open position by the latch 2| and the movable coil I0 of the relay is in its lowermost position,. as shown in Figure 2, the position assumed when the circuit, of the coil III is opened, as hereinafter described. When this coil is energized and is repelled from the stationary coil 49 of the relay, as hereinafter described, the switch will be tilted about the pivot II without disturbing the connection between terminals 46 and 41, as shown in Figure 7. An additional terminal 50 enters the same end of the switch tube as the terminal 41 and is separated therefrom so that when the switch I6 is in the position described when the secondary coil I9 is de-energized, the`mercury 48 in the switch I6 will be out of contact with said terminal 50, but when the coil III has been repelled to tilt the mercury tube switch to the position shown in Figure 7, the circuit will be completed between the terminals 41 and 50 by the flow of the mercury 46 to that end of the switch to submerge terminal 59.

From the schematic wiring diagram shown in Figure '1, vit will be seen that the lead L from the commercial line passes through binding post 5I and through terminals 41 and 46 when the switch is tilted to the position shown. in Figure 2 with the coil III resting upon the coil 49 and `from terminal 46 to binding post 52 and from thence through the windings of the primary coil 49 of the relay to the binding post 53 and from thence to lead L' back to the commercial line. The windings of the secondary coil III are placed in circuit' by lead 54 through binding post 55 and lead 56 through the room thermostat R to binding post 51 and from thence by lead 58 through the resistance winding 4I of the heating element to binding post 59 and from there through lead 60 to the other end of the winding coil I0. When the room thermostat is open, the secondary circuit will be broken and the coil IIl will rest upon the coil 49. When the room thermostat closes the secondary circuit through coil I0 it will be repelled, as shown in Figures 4 and '1, thereby closing the circuit between terminals 41 and 50 so that the commercial current will then pass through binding post 6I, motor M, binding post 62 and back through lead L to the commercial line. When the room thermostat is first closed, the heating element is received entirely within the thermal member, as shown in Figure 2, and when the room thermostat closes the secondary circuit, the heat produced by the resistance coil 4I of the heating element will cause the latch pin to disengage the member 30 whereupon thelatch 2| will release the switch tube I6 to rotate to the open position, as shown in Figure 5, unless combustion occurs within a predetermined time which is suilicient to cause the thermal coil 3 responsive to combustive conditions to rotate the carrier plate 9 to remove entirely the heating element from the thermal member 3l, as shown in Figure 4. Should at any-time after combustion has been initiated and the secondary circuit closed through the room thermostat R., the combustion fail or cease from any cause whatsoever, the thermal 3 responsive to combustive conditions will cool and cause the carrier plate 9 to rotate in the opposite direction and move the heating element to be received entirely within the thermal element, whereupon the free end of the portion 32 of the thermal member will move outwardly and release the tripping mechanism to allow the switch I 6 to open all circuits ltherethrough causing a shutdown of the burner mechanism until the switch I6 is reset.

Although the disclosure of this invention has been confined to the descriptionof its application with devices used in connection with the control of iiuid fuel burners, the extent of its use is by no means limited to that eld alone.

The disclosure of means whereby a normally closed releasable switch may be held closed or released under certain conditions need not depend solely upon the temperature responsive helical coil operated mechanisms, as shown, for actuating the heating element. Other means for moving the heating element or shielding itk are suggested in the patents referred to inthe introduction.

What I claim is:

1. In a circuit control, a switch, a relay for opening and closing the switch, releasable means normally maintaining the switch in operative relation to the relay, a thermally actuated tripping device for the switch adapted to release the switch to open independently of the relay, a freely movable heating element adapted to operate the tripping device when in operative relation thereto, in combination with a temperature responsive device including an operating shaft adapted to be rotated in opposite directions upon variations of temperature, a plate mounted thereon for movement therewith. said heating element mounted upon a guide normally directing the freely movable heating element by gravity into operative 'relation with the tripping device, and means upon the said plate to engage and bodily move the heating element out of operative relationship upon rotation of the operating shaft in one direction and allow the heating element to assume the said operative relationship upon movement in the opposite direction.

2. Means to control the operation of a switch. including electrically operated means to open and close said switch, and releasable means normally maintaining the switch in operative relation to the first means including a thermally actuated tripping device adapted to release said second means to openindependently of said iirst means, afreely movable heating element adapted to operate said tripping device when in operative relation thereto, and a temperature responsive device independent of the heating element for bringing the zone of heat from the heating element into and out of operative relation to the tripping device.

3. Means to control the operation of a switch, including electrically operated means to open and close said switch, and releasable means normally maintaining the switch in operative relation to the first means including a thermally actuated tripping device adapted to release said second means to open independently of said ilrst means, a freely movable heating element adapted to operate said tripping device when in operative relation thereto, movable means to increase and decrease the transfer of heat from the heating element to the tripping device while the heating element is energized, and means responsive to temperature changes independent of the heating element to actuate said movable means.

4. In a circuit control, the combination of;a first switch and a second switch, a transformer relay for actuating said switches, a circuit to be controlled including the rst switch, a circuit for the relay including the second switch, releasable means normally maintaining the switches in op.- erative relation to the relay whereby the rst switch may be opened and closed while maintaining the second switch closed, a third switch for controlling the operation of the relay in the secondary circuit of the relay, a thermally actuated tripping device for the releasable means adapted to release said means to open the rst and second switches independently of the relay, a freely movable heating element adapted to operate the tripping device when in operative relation thereto, and means to control the relative proximity of the heating element and tripping device.

IRA E. MCCABE. 

